Lumpy Setting Compounds

Q.When we're working with what we call "hot mud"— setting-type drywall compounds that come in powdered form — it seems almost impossible to mix the stuff up without getting lumps. Do you have any suggestions for smoothing out the consistency?

A.Myron Ferguson, a drywall contractor in Broadalbin, N.Y., responds: A setting compound is similar to a plaster product — the fresher the product and the cleaner the water and the mixing container, the more consistent the final mixture will be. Powder stored in bags that have been open and exposed to high humidity tends to clump together, which can lead to a lumpy mix. Mixing with very cold water can also lead to lumps, I've found.

For best results, start with fresh compound that's at room temperature, and add it slowly to water that's also at room temperature. Always add the compound to the water — rather than the other way around — and start with a thin mix, then add compound a little at a time until you've reached the proper consistency. Let it slake for a minute or so, then remix before using.

For small batches, I just mix the compound in a pan with a small taping knife. A small mixer (used for mixing cakes) chucked into a drill works great for mixing small batches, too (see photos).